Officers responded to a report of a man down on Alvarado Niles Road near Union Square at about 6:10 a.m., according to Union City police.
Arriving officers found a male victim who appeared to have been struck by a vehicle traveling west on Alvarado Niles Road, police said.
The victim was pronounced dead at the scene.
The driver and vehicle involved in the collision had not been identified as of Sunday afternoon.
Anyone who might have informnation regarding the incident is asked to contact Union City police at (510) 471-1365.